Effect of an Out-of-Pocket Insulin Cap in Medicare Part D

Introduction Out-of-pocket (OOP) costs can often impede patients’ access to prescription drugs. The Inflation Reduction Act of 2022 (IRA) limited OOP costs for insulin products covered by the Medicare Part B and Part D programs to no more than $35 for a one-month supply. Methods This analysis uses prescription drug data from Medicare Part D and commercially insured patients along with a difference-in-differences specifications to estimate changes in OOP costs among Medicare Part D enrollees after policy implementation. Results We estimate that the Part D enrollees most likely to be affected by the policy saw a $34.71 reduction in average OOP costs per prescription across all insulins compared to what might have occurred absent the policy in 2023. Conclusion These findings suggest that targeted limits on OOP costs for high-value drugs can reduce cost burden for patients.